Tuning negative and positive magnetoresistances by variation of spin-polarized electron transfer into π-conjugated polymers

Feng Luo; Wei Song; Zhe-Ming Wang; Chun-Hua Yan
March 2004
Applied Physics Letters;3/8/2004, Vol. 84 Issue 10, p1719
Academic Journal
A series of polyparaphenyl derivatives with different conductivities have been synthesized to fabricate three kinds of polymer-embedded La[sub 0.7]Ca[sub 0.3]MnO[sub 3] (LCMO) composites by mixing different weight fractions of polymers and LCMO. X-ray diffraction and Fourier transform infrared spectra show the coexistence of the LCMO particles and polymers and no chemical reactions between each other. By adjusting the conductivity and π electron polarization of polymers, spin-polarized electron transfer from the surfaces of LCMO magnetic particles through the interfacial coupling into polymers can be tuned, leading to the tunable negative and positive magnetoresistances in these composites. This abnormal positive MR can be mainly attributed to the spin-polarized electron tunneling weakening and magnetic scattering enhancement on polarized π electrons through the LCMO/polymer interfaces. © 2004 American Institute of Physics.


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